This invention relates in general to an apparatus and methods for controlling the administration of radiation to a patient, and more particularly, to stereotactically directed radiation apparatus and radiation therapy and surgery performed by the apparatus.
The use of a computerized tomographic (CT) scanner or a Magnetic Resonance Imaging (MRI) system has been generally used to aid in diagnostic procedures or to aid in planning placement of a patient prior to the patient receiving radiation. The patient was then removed from the CT or MRI unit and radiation therapy was performed on a secondary system physically removed from the scanning facility. The employment of a second apparatus was due to the fact that the radiation levels necessary for radiation therapy were incompatible with the levels required for diagnostic procedures. The secondary radiation (scatter) from the treatment system required that it be placed in a separate, shielded room. Attempting to successfully reposition the patient in the secondary device, along with potential physiological changes which may occur in the patient, can cause considerable problems in insuring a successful outcome with minimal danger to the patient.
Radiation therapy has generally been practiced utilizing either a Cobalt 60 radioactive source (1.2 MeV energy) or a linear accelerator with electron energies ranging typically from 4.0 to 20 MeV. Most existing radiation therapy technology provides radiation from a single focal point. Custom shielding blocks, and beam shapers are necessarily utilized in most treatments to deliver a uniform dose to the target without overdosing the surrounding area of healthy tissue. The radiation field size which is emitted from the device is typically controlled through movable collimators. This type of system has several severe limitations; the dose delivered to the area surrounding the target site receives as much or more radiation as the target itself. The limiting factor in treating tumors in many instances is the radiobiological effect, e.g., tissue damage, which may be delivered to the surrounding healthy tissue. In many cases radiation therapy will be more effective if higher doses of radiation can be directed to the target site without subjecting the surrounding area to toxic amounts of radiation. Current practice typically incorporates laser positioning systems to determine patient location prior to treatment. This positioning is confirmed and recorded by placing a tattoo on the patients skin. The accuracy of this procedure requires that a treatment xe2x80x9cmarginxe2x80x9d be included to compensate for the following types of factors: a) mislocation of a patient; b) growth of the target during the treatment program (which may take up to six weeks); and c) physiological movement of the position of the target between treatments (several days can elapse between treatments). Also, in treatments to date patients are administered radiation in a static modality, and the patient is not moved during the administration of radiation during treatment.
Current technology for therapy systems requires that external shielding, typically 24-60 inches of reinforced concrete, be utilized to prevent generalized exposure to the scattered radiation present in the treatment room. The requirement for this shielding has restricted treatment rooms to locations in facilities which can support the resulting high floor weight loadings.
This invention features a stereotactically directable radiation therapy system (the system) for administering radioactivity to a patient. The system provides lower skin doses of radiation and improved targeting localization of the primary radiation dose to a patient. The system is designed to be fully integrated so as to provide a high degree of interface between the diagnostic, planning, and treatment phases. A radiation source beam unit which allows for increased radiation delivered to a tumor while decreasing the radiation received by surrounding tissue is provided. A radiation beam catcher which is lightweight and absorbs at least 80% and preferably at least 90% of the emitted radiation is also provided. Methods of performing radiation surgery and radiation therapy on a patient utilizing the apparatus of the present invention are also provided.
The system comprises: a) a CT Unit, or in an alternative embodiment an MRI Unit. Commercially available CT and MRI units, as would be known to those in the art are suitable. Further, any means allowing for the visualization of the interior and surface of a patients body (a patient 3-D mapping means) which encodes the information derived from the patient such that the information may be further utilized to control the administration of radiation by the system to the patient, as would be known in the art, is an acceptable component of the system. Any references to particular visualization means such as a CT scanner should be understood to be a preferred embodiment and not limiting of the scope of the invention. A CT scanner is preferably used to analyze hard tissue, for example, bone. An MRI unit is preferably used to analyze soft tissue, for example, the liver; b) a radiation source beam assembly (RSBA); the RSBA comprises a rotatable radiation source support means, in preferred embodiment a C-arm gantry, a radiation source beam unit (RSBU) affixed to the rotatable source means, a radiation yielding means, preferably a Tungsten collimator. The CT or MRI unit is affixed opposite the radiation source beam unit, d) a treatment table which has four degrees of freedom of movement, and e) a command and control center (xe2x80x9cCCCxe2x80x9d) the CCC comprises a central processing unit (xe2x80x9cCPUxe2x80x9d), the CPU may be any commercially available, for example, a pentium(copyright) chip. Any processing means which can manipulate the information received from a patient visualization means, for example, a CT unit, so as to control the administration of radiation to a patient by the system is suitable. The CCC includes treatment software which is commercially available, as would be known to those in the art, or alternatively specially modified software may be utilized. The CCC also comprises a control panel which allows one to, for example, position the patient on the treatment table and to preset treatment exposure times. The exposure time is controlled by an FDA approved timer or similar means as is known in the art. The CCC also comprises means for displaying information, for example, regarding the positioning of the treatment table and the elapsed time of treatment. A cathode ray tube or other display means and a mouse may also be included as part of the CCC. In an alternative embodiment the system further comprises a pedestal controller or similar in-treatment-room control means located in the treatment room. The pedestal controller is used to move the treatment table from within the treatment room.
The CT unit is located opposite of the RSBU, thereby providing for the ability to perform the necessary target localization procedure on the patient without any need for the patient to be removed from the table. The treatment software program processes the CT data, provides target localization data and allows a radiation treatment therapist to outline a target""s margins xe2x80x9con-screenxe2x80x9d. The software provides dose planning, and defines treatment parameters.
The system incorporates multiple individual radiation sources, in a preferred embodiment seven Cobalt 60 sources. The focus of the individual beams emanating from the radiation sources intersects the target at a specific point relative to the central source position, preferably about 56 cm and initially contacts a patient a point relative to the central source position. preferably about 40 cm. A source holder assembly is secured in position and securely affixes the radiation sources in position to eliminate any focusing errors of the source beams. A rotating collimator positions the desired beam profile for the source beam position. The collimator movement preferably is accomplished within 1.5 seconds. The resulting sphere of radiation at the intersection of the beams is defined as the xe2x80x9ctreatment zonexe2x80x9d. This treatment zone encompasses spheres of radiation of varying diameters. In a preferred embodiment these diameters are 6.0, 14.0, 18.0 and 30.0 millimeters. By incorporating multiple intersecting radiation beams the system delivers a more intense radiation treatment to a defined target, while minimizing the radiation received by adjacent healthy tissue.
The system incorporates a xe2x80x9cradiation therapy beam catcherxe2x80x9d which captures greater than 80% and preferably greater than 90% of the primary and scatter or penumbral radiation from the radioactive source material.
The xe2x80x9ctreatment tablexe2x80x9d is an integral part of the system. It can be controlled either by a joystick or directly by the treatment program software. Commercially available multimodality and 3-D planning and targeting software is suitable for this purpose. The joystick may be controlled by a DC stepper motor.
In another embodiment, the automatic positioning of the treatment table will also provide for xe2x80x9cconformal therapy.xe2x80x9d
By xe2x80x9cconformal therapyxe2x80x9d is meant the process wherein a target which is larger than the treatment zone of the radiation sphere will be sequentially positioned until the entire target has received the designated dose of radiation imparted by the radiation sphere. The treatment table is preprogrammed to initialize the X, Y and Z coordinate positions so that the absolute table position relative to the radiation sphere is known to a predetermined accuracy, preferably of xc2x10.1 mm. The positioning of the table is verified through two modalities, a position transducer, and a shaft encoder, similar position verification means may be utilized. Both units verify position to a predetermined accuracy, preferably of xc2x10.1 mm and must agree, within set parameters at all times for the treatment table and RSBA to operate. A movable head frame may be included as necessary to allow for radiosurgical procedures on, for example, brain tumors. By xe2x80x9cradiosurgeryxe2x80x9d or xe2x80x9cradiosurgicalxe2x80x9d, is meant the application of radiation to a patient in a single treatment session. In contrast, xe2x80x9cradiotherapyxe2x80x9d is the administration of radiation to a patient in more than one treatment session.
Other and further objects, features and advantages will be apparent from the following description of the presently preferred embodiments of the invention.